Sahih Muslim Book 6, Hadith Number 2469.

Chapter : Permissibility of observing the fast or not observing it in the month of Ramadan for a traveller.

A Hadith like this has been transmitted on the authority of Ibn Shibab who said that they (the Companions of the Holy Prophet) followed the latest of his commands and looked upon it as one abrogating (the previous ones) and the most firm.